Electric tube evaporating apparatus



July 2, 1935. C' KAYKO ET L 2,()06,771

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Win/Ess www' lO Sheets-Sheet lO THEME YS Patented July 2, 1935 UNITED -STATES ELECTRIC TUBE EVAPORATING APPARATUS Charles J. Katyko and C. Gaylord Hall, Jackson,

Mich., assignors to The 'Sparks-Wilmington Company, Jackson, Mich., a corporation of Ohio Application July 13, 1931, serial No. 550,488

28 Claims.

This invention relatesV to yimprovements in an electric tube evacuating apparatus in which a plurality of heating elements co-operate with vacuum-producing means for vdrawing moisture i and occluded gases from the glass and metallic units within the tube.

The main objects of this invention are to provide Aa machine of the above-mentioned class which will be rapid, economical and accurate lo in operationand that may be economically, simply and compactly constructed.

In carrying out these objects, we have constructed a machine wherein the tubes are continuously moved during the evacuating process, thus eliminating the time necessarily consumed in the usual intermittently operated exhaust device, in starting and stopping and also during the vertical movements of the bombardment coils when being brought into and out of operative relation with the tubes. The vacuum pumps vare mounted in close relation with the tube exhaust ports which permits a very short connection between the tubes and pumps thereby eliminating long and complicated connections vwith .evacuating time. Furthermore, there is'an individual pump for each tube exhaust port-which eliminates tube waste if a leak occurs by preventing the destroying of a number of tubes at a time, as happens in other types of exhausting machines where a plurality of tubes are connected with each pump unit.

'I'he vacuum pump units are all mounted independently of each other and in such a manner as to permit the ready replacement of any one of. these pumping units without in any way' interfering with the operation of the remaining units in case of accident or breakdown. We obtain further economy by using three-phase relatively small motors for operating the vacuum pumps which eliminates starting windings on the motors, large feed wires, trick throw-out switches, etc.

Another object is to conserve energy by providing simple means for automatically shutting 01T the respective pump motors during the unloading and loading of the tubes.

Still another object is to eliminate mercury fumesl by providing means for cooling the mercury cups through which electrical connection is made with the tube iilaments.

A further object is to provide simple and eili- `cient means for automatically sealing the tube whereby the seal-off tube will be cut in close proximity to the base of the tube.

(Cl. Z-275) A still further object is to provide an exhaust apparatus which may be easily and quickly adjusted for diierent types and sizes of electric tubes. l'

Other objects and advantages relating to the 5 details of the structure and the form and relation of rthe parts thereof will more fully appear from the following description, taken in connection with the accompanying drawings in which:

Figure 1 is a top plan, partly broken away, of 10 an apparatus embodying the various features of this invention.

Figures 2 and 3 are enlarged detail sectional views taken respectively on'lines `2 2 and 3 3, Figure 1, illustrating one of the pump units and manner of mounting the same on the machine.

Figure 4 is an enlarged transverse vertical sectional view taken substantially on line 4 4, Figure 1 Y,

Figure 5 is aihorizontal sectional View taken on line 5 5, Figure 4, in the plane of the top of the stationary table, with various portions broken away to more clearly disclose certain of lthe underlying parts. the resultant leakages and thus shortening the Figure 6 Vis an enlarged detail inner face view of adjacent ends of a pair Aofthe segments comprising .the outer electrical pick-up bar for. supplying current to the tube lament, taken substantially-on line 6 5, Figure 5, and illustrating the manner of mounting these segments in in- 30 sulated relation. 'A

Figure 7 is va sectional view taken on line 1 1,

Figure 6;

Figure 8-is an enlarged transverse vertical lsectional view through the oven and one of the tube 35 exhaust ports taken on line 8 8, Figure 1, and illustrating the manner of connecting the tubes with respective vacuum pumps.

Figure 91is a horizontal sectional View taken in the plane of the line 9 9, Figure 8. 40

Figure 10 is a vertical sectional View taken on line lll-l0, Figure 9.

Figure 1'1 is a horizontal sectional View taken on line Il l l, Figure 8. t

Figure4 12 is an enlarged detail vertical sectional `vieW taken in the plane of the line |2 I2, Figure 5, illustrating the manner of mounting the collector brushes for the motors for the pump units.

Figure 13 is an enlarged vertical sectional view- 50 taken in the plane of the line |3 |3, Figure 12.

Figure 14 is an enlarged detail vertical section takenon line |4 l4, Figure 5, illustrating the manner of electrically connecting the inner pickup bar with'the'return bar. 55

-taken on line 26-26, Figure 25.

taken ou line 31-31, Figure 36. i s l vFigure 38 is a vertical sectional-,view taken on line 313-38, Figure 36. Y

Figure is a detail sectional view taken on line l5-l5, Figure 14.

taken substantially in the plane of the line lli-I6,

Figure 5.

Figure 17 is a sectional view taken on theline ll-l, Figure 16.

Figure 1s is a horizontal detaii 'sectional viewV through the rear end of the oven, taken on line. |8-I8, Figure 4.

Figure 19 is an enlarged detail vertical sectional 7 VView through the rotary table' taken substantially in the plane of line lil-I9', Figure', andillus'- trating in elevation, one of the pump motor control units together'with the automatic throw-outv and starting members. l

Figure 20 is a vertical sectional view through the three wire connector taken on line 2li-20, Figure'19.

l? Figure 21 is a horizontal sectional' vview-through one of the motor switches and the throw-out member taken on line 2|-2I, Figure 19. Figure 22 is a similar view to Figure 21,-taken substantially on line 22-22, Figure 19, showing one of the motor switches in connection with the automatic starting member.

Figure 23 is a face view of one of the pump f motor three-wire control switches.

. Figure 24 is an enlarged sectional view taken on line 24-24,- Figure 23.

Figure 25 is a detail transverse sectional'view ,taken in the plane of the line 25-25, Figurev 5,

illustrating the water connections for the water manifold.

Figure 26 is a detail horizontal sectional view Figure 27 is a diagrammatic View the electric circuit for each pumping unit motor.

Y Figure 28 is an enlarged vertical sectional view :through the bombarding carriage taken in the 'piane of the line 2li-2s, Figure 1.v

f Figures 29, 30 and 31 are enlarged vertical sectional views taken respectively on lines 29-19,

`Figure32 is a side elevation of the rear porltion of the bombarding carriage showing `por- -tions thereof broken away to better disclose the actuating means.

Figure33 is a horizontal sectional view taken in the plane of the line 33-33, Figure Figures 34 and 35 are vertical sectional views ,taken respectively on' lines 34-34 -and. SFF-35,

Figure 33. A

Figure 36 is a top plan of' the forward end of the bombardment carriage showing the seal-off mechanism.

Figure ai is uV vertical dessu Vsectional view Figures 39 and 40 are detail vertical sectional Vviews taken respectively on lines 39--39 and 40--40, Figure 36.

Figure 41 is a. horizontal sectional viewtaken 'on line 4I-f4l, Figure 39.

Figure 42 is a, transverse verticalsectional view taken on line 42--42, 'Figure 36.

Y member supporting bracket is hingedlymounted.

l The machine illustrated inthe drawings is s adapted more particularly for evacuating electron tubes containing a plurality of metal parts such stationary table.

illustratingk as a filament, plate, grid, etc. as used in radio tubes, and is comprised of substantially four units, namely, a, vacuum-producing or pumping means, a heat-producing medium for treating the glass tubes and filaments, an electrical bombardment means for heat treating the metallic portions of the tube such as the plate, grid etc., and a seal-off means closing and severing the seal-off tube, all of which function for successively and continuously treating the tubes as they travel through the machine from the kstarting position to the finish or seal-oil position.

These units are mounted upon and supported by acircular stationary table and a rotary carrier mounted for movement in a plane below the Upon the rotary carrier is mounted to move therewith the pumping units together with the tube-supporting exhaust ports.

exhaust ports, with the tubes continuously movedin sequence'therethrough and a. bombardment carriage.

. The oven, in this instance,` extendssubstantially two-thirdsv the distance circumferentially -over the stationary table and is provided with suitable heat-producing means for causing` a sufficiently high temperature in the oven for baking `the glass bulb as the tubes are passed through the oven to such an extent as to free the glass of the absorbed gases. K

. The carriage is mounted for oscillatory movement upon the stationary table atv the discharge end of the oven and is provided with suitable fixed bombarding coils between iwhich the tubes are caused to travel as they are. being continuously .moved awayvfrom thedischarge end of the oven.

VAs the tubes pass between the coils,.they are subijected to powerful high frequency currentsinduced by the coils. The intense heat thus created in the metallic parts of the tube frees said parts of the. occluded gases which are immediately evacuated from the tubes by the pumps. The

tubes then pass between Aanother pair of coils carried by the carriage and which are positioned at the level of the getter cup which flashes a gas- `absorbing element such as magnesium, barium or the like.

The seal-off mechanism is operably secured to vthe discharge end of the carriage for auto- .matically severing the seal-off tube as the vac- .uum tube passesV from the bombardment zone after which the tubeV is replaced by an unex- Vhausted tube.

Referring now more specifically to thefcon.-4 struction of the apparatus as disclosed in the drawings, I represents a vertically disposed base having its lower end curved outwardly to form an annular supporting flange 2. The upper end of the basehas an inwardly extending annular flange 3 upon which is mounted an upwardly extending tubular column 4 which, in turn, has the upper end thereof provided with an inwardly extending fiange 5 for supporting a pluralityrof, in this instance nine, outwardly extending radial arms 6, see Figures 1' and 4. n f

These arms 6 extend across the upper end of vthe column 4 and are secured thereto by bolts or screws l screw-threaded in the flange 5I and by asupporting spider 8 positioned within the upper end of the column 4 with the ends of the arms thereof engaging the underside of the flange 5 and to which the inner ends of the arms 6 are secured by suitable bolts or screws S. The outer ends of each of the arms 6 terminate in a vertically extending head 6 to which is adjustably secured an inverted U-shaped bracket II) by means of a pair of screws Il passing through elongated slots provided in the head 6 and screwthreaded in the adjacent side of the bracket.

The arms 6 and the brackets l5 are for the purpose of supporting the stationary table as I2, see Figures 4 and 5. The table i2, in this instance, consists of a pair of concentric annular supporting plates I3 and I4 positioned concentric with the base l and a pair of similar plates I5 and I5 composed' of any suitable insulating material such as that commonly known as transite or the like.

The supporting plates 3 and I 4. are disposed in a horizontal plane in radial spaced relation with each plate positioned beneath a respective leg I0 of the brackets IB while the insulating plates I5 and i5 are positioned over a respective supporting plate and are secured to said plates and to the supporting brackets I!! by means `of bolts or screws I7 passing through registerlng holes in the brackets and adjacent insulating plates, and screw-threaded in the respective supporting plates, as shown more particularly in Figure 4. These insulating plates I5 and I5 have their adjacent edges extending inwardly beyond the adjacent edges of the supporting plates I3 and I4 for the purpose of supporting a lpair of electric pick-up bars i8 and I9 composed of brass or other suitable material equally well adapted for conducting electricity, see Figures 4 and 8. These bars i8 and I9 may be secured to the respective plates l5 or l5 in any suitable manner as by bolts or screws and are arranged to extend circumferentially of these plates with their inner vadjacent edges in vertical alignment with the inner adjacent edges of said plates for the purpose of permitting a continuous electrical connection with each'of the tube exhaust ports during the rotation of said exhaust ports in a manner hereinafter more fully explained.

Mounted upon the table i2 is the oven 22 which is maintained in position upon said table by the brackets ID through which the furnace passes.

The furnace, in this instance, is inverted U- shaped in cross section and is composed of an outer and inner case 23 and 24 respectively which are insulated from each other by any suitable insulating material such as'mineral wool 25.

The cross section of the furnace is substantially the saine inform and size as the inner cavity of the brackets I so that when said brackets and the stationary table are secured together, the oven 22 will be securely clamped therebetween.

, The furnace, as hereinbefore stated, extends circumferentially over a greater portion of the table I 2 and has the lower end thereof partly enclosed by the insulating plates i5 and I 5 of the table I 2 which extendinivardly Some distance beyond the respective sidewalls of the furnace so as toform a bottom for the inner chamber as 26 in the furnace having the lower or bottom side thereof provided with a circular slot 2 extending circumferentially from one end of the furnace to the other. As shown, this slot extends entirely around the stationary table I2V for permitting the tubes to extend through said table andinto the furnace during the continuous movement of the tubes.

The ends of the furnace are. closed by suitable end plates 2S slidably mounted in vertical guides 29 secured to opposite side walls of the respective ends of the furnace, see Figures 4 andA 18. Each of these end plates 28 is provided with an opening 30 which extends upwardly from the lower edge thereof and having the contourv thereof conforming with the contour of the tubes for permitting the tubes to be continuously moved into and out of the oven through said end plates.

Any suitable means may be utilized for producing the required amount of heat in the oven 22 such as electrical heating elements, or as shown in the drawings, the oven may be provided with perforated tubes or burners E2 which are, in this instance, arranged in three sets of two tubes each with a tube of each set positioned at the bottom of the oven chamberl' adjacent the outer and inner wall of said chamber, two of the sets of tubes extending inwardly from respective ends of the oven to substantially a' third of the distance around the chamber 25 while the third set of tubes is positioned at the central portion of the oven between the two outer positioned sets of tubes, as illustrated more clearly in Figure l, for producing a uniform name throughout the oven chamber.

' The gas may be supplied to the burners under pressure through suitable conduits or pipes 35 which are connected with any suitable source of gas'supply not shown, by a common conduit 36 to which the conduits 35 are connected.

rThe conduit 35 may be provided, as shown in Figure l, with a suitable valve 3'! for controlling the supply of gas to the tubes 35, and the tubes 35 in turn may be provided with-suitable valves 33 for controlling the amount of gas supplied to the burner tubes 32 connected therewith. Any suitable means for supplying air to the burners 32 may be provided such as the pipes 34 which are, in turn, connected with a common air supply pipe 39 adapted to be connected with a pump not shown or other suitable means for supplying air A provided with a plurality of in this instance two, i

openings 43 which may be closed by suitable cover plates i4 formed with insulated spaced walls similar to the construction of the walls of the oven 22 and which are adapted to extend into the openings 43 for preventing the escapement of heat through said openings.

Carrier Below the stationary table E2 is a rotary carrier composed primarily of a rotatable table 45 and a tube carriage Mt. The rotary table 45 is mounted in a horizontalplanenear the base of the column 4 and is provided with a central opening therethrough for receiving the lower enlarged `portion. 4 of said column. The table 45 is mounted for rotation upon a ball-bearing 46 which is ymounted'upon the upper surface of thefiange 3 of the base l.

The,table' is rotated, in this instance, by means of a ringgear 4'I secured to the outer Vperiphery of a. dependent annular flange 48 `ecured to or made integral with ythe table 45 and which surrounds the bearing member 46.

A pinion 49 for drivingthe gear 41 is secured tothe upper end of a vertically disposed vshaft 50 which is rotatably mounted in a suitable bearing'5I secured to the base I by'screws 52 or their equivalent, as shown more clearly in Figure 4.

The lower end of the Vshaft 50 is operably connected with a suitable speed-reducing gearing 53 which is mounted on a horizontally disposed bracket 54 secured by screws 54 to the vertical portion ofthe base I below the bearing member 5I.v The driveshaft as 55 for the speed reducing gear 53 extends outwardly, inthis instance, in a horizontal Yplanefromfsaid gearing, and has secured to the outer end thereof a pulley 56 which is connected by asuitable belt 51 to the drive pulley 58 mounted upon the armature shaft of a motor 59 secured to 'the flange 2 ofthe base I.

The outer edge of the table 45 terminates some distance Within theVV vertical plane of thestationary table I2 and is provided with apendant ilange c or skirt 60 which has the outer peripheral surface thereoflformed with a plurality of, in this. instance twenty, flattened surfaces 6I formed at right angles to a radial line passing through the ures 2, 3 rand 4.

c'enterthereof, see Figure 5. These flattened portions 6| are for the purpose of supporting a respective pump unit 62 which, in this instance, consists of .a supporting bracket 63, an electric motor 64 and a pair of vacuum pumps 65, see Fig- The motor 64 is secured to aV plate 65 which has one end thereof pivotally connect-ed at one side Vat 61 to downwardly extending lugs 68 formed on 'to the table 45 by means of a pair of screws 13 n Awhich pass through respective slots 14 provided in the vertical portion 63" of the bracket 63 and *.is screw-threaded in the apron 69 of the-table 45. Each of the slots 14, in this instance, has

` the lower portion thereof enlarged to receive the i has been provided the following novel construction for supplying electrical energy to these motors and which is illustrated more. clearly in Vhead of the respective screw 13 so that all vthat is necessary for removing the pump unit .from the table V45is to loosen the screws 13 sufliciently to permit the pump unit to be raised until the heads of the screws are in registration with' the enlarged portion of the slot 14 whereupon the pump Vunit may be readily removed, and it is evident that a pump unit may be as readily secured in place to theV table 45 by the reverse operation. Pump motor circuit It will be'readily understood thatv the Apump units62 will be continuously rotated by the table `45, and in order to continuously operate each of these pump vunits during the rotation of the table 45 and' independently of each other, there Figures 4, 12, 13, 19 to 24 inclusiveand Figure 27. of the drawings.

Each of the motors 64 being a three-phase motor, we haveprovided a brush unit 16 which is supported upon a bracket 11 in insulatedrelation thereto, said bracket being secured 4by screws 18 to the vertical portion oi the base I at any convenient location as at the rearV thereof. as shown more clearly in Figures l and 12.

The brush unit'16, in this instance, is provided with three brushes 19 which are pivotally mounted at 88 to a respective metal base 8|, said brushes and bases being arranged in electrically spaced relation upon supporting plates 82 composed of insulating material, and each base 8| is provided with an electric terminal 83 adapted to be conveniently connected to one end of a wire 84 leading to a suitable source'of potential not shown. The upper ends of each of the brushes 19-,are

yieldingly maintained in sliding contact with a respective bus-bar 85 by means of a comprsion spring 86 having one endipositioned in arsocket 81 provided in a brush support 88 with which each brush proper is connected and the other end resting upon the adjacent portionof the base 8|.' as shown more clearly in Figure 13. 1

The bus-bars 85 extend concentrically-y about the base I in radially spaced relation from each other, and they are secured in electrically spaced Y relation to the underface of a bus-bar supporting ring V89 which is composed of any suitable insulating material such as ebonite or .the like.

VThis bus-bar supporting ring 69 is, in turn, se-V cured to a plurality of, in this instance twelve,l

insulating spacing blocks 90 which are Asecured in uniform circumferentially spaced relation to the underside of the table 45'A between the flange l 48 and apron 69 by means of screws 9|.

It will now be understoodthat the brushes 19 being secured to the `base I, will remainv ina xed position, while the bus-bars 85 being secured to the table 45, will be rotated thereby in xed relation with the pumping units 62, and b`y electrically connecting each of the pumping unit motors 68 with the bus-bars 85, electrical energy may be continuously supplied vto each o1' said motors, and in accomplishing this result, we utilize a three-wire connector 92 which is illusure 21, and which in this instance consists of a pair of terminal supports 92' and 92 composed of any suitable insulating material, and each of these terminal supports is provided with three terminal units 93 and 94 respectively which are adapted to be removably connected with each other. One of the terminal supports as 92 is.

connectedV by screws or otherwise to the skirt 6| of the table 45 adjacent the respective pump Yrelative tothe brushes 19 but will be maintained 45 trated in Figure 20 and diagrammatically in Figunits, while the other terminal support 92'( is f frictionally maintained in operative relation with the terminal 92' `by the engagement with each other of the terminals 93 and 94`thereby per- Y mittingk the ready connecting or disconnecting of or de-mounting the pump umts.

Each ofthe connectors 92 has one set of terminals 94 thereof connected in circuit to a respective set of brushes of, thel corresponding pump motor 64 while the other set of terminals 93 of the Lconnector isconnected in circuit with respective contact members of `a three-phase four-wire 440 volt contactor 95, see Figure 27.V

Each of thecontactmembers as 96, 91, 98 and 99 of the contactor is maintained in electrical connection with respective terminals |00, IUI, |92 and |93 by means of a relay |04 which is normally maintained in an energized condition by a current passing from one of the bus-bars 85 through 1(i0 the circuit wires for the motor when mounting Y the terminalv 03, contact. member 99 and wire a to a respective terminal unit 93-94 of a second three-wire connector S2 constructed similarly to the hereinbefore mentioned connector 92 for the motors 64 and which is shown as being connected adjacent the respective pump unit upon the outer edge of the pump bracket 63, Figure 4.

From the terminal unit 94, the current passes through a wire b and a manually operated switch s and wire c to a second terminal unit 63-94 of the second-mentioned three-wire connector. 92 and thence through the wire |05, cut-out switch |06 and wire 6? to the relay |64 and thence to the ground circuit of the motor S as shown. f v e It will be noted that the switch s is normally maintained in the closed position so that if, at any time, it is desired to stop the operation of the motor 64 and pump connected therewith in case the pumping unit breaks down or fails to properly function for any reason, the operation of said unit may be discontinued independently of the remaining pump units and the respective unit replaced ,without in any way interfering with the operation of the remaining units by merely opening the switch s which will break the circuit passing through the relay |04 causing said relay vto be de--energized and permitting the contacter 95 to move to the open position thereby breaking the circuit for operating the respective motor 61h If, however, the circuit for any one of 'the pump motors 6ft is broken, said pumping unit controlled thereby is idle due tothe respective relay |04 becoming cle-energized withthe consequent opening of the respective contacter 65, and if it is desired to put said pumping unit` into operation, all that is necessary is to cause the energizing of the relay |04 by closing a manually operated switch 1- connected in series with the cu*- out switch ESG, When the switch r is closed, the current then wiil pass from one of the bus-bars through the terminal |63, wires H3 andud through a respective terminal unit S13-94 of the second-mentioned three-wire connector 92 4and thence through the switch fr, line c, terminal units 93-94, wire 65 andthence through the normally closed cut-out switch m6 and wire |97 to the frespective relay |611 andthen to the ground circuit leading from the motor 64 whereupon the relay H34 will again become energized and cause the closing of the respective contactorV which will again estabiish a current through the respective pump motor 5t and cause the respective pump unit to resume operation.

As hereinbefo-re stated, there is one of the automatic cut-out and starting switches foreach pump unit and they are constructed in the following manner: A base as li, Figures i9, 2l, 22, 23 and 24, composed ci suitable insulating material such as ebonite or the like, is secured to Va plate which, in turn, is secured to the skirtl of the table 45 in proximity to the corresponding pump unit. Y Y

Upon the base iii? is mounted in spaced relation a pair of contact members l2 and i3 which consists of relatively thin narrow strips of spring metal with their intermediate portions bent Vto extend outwardiy to form respective cam members |51 i i 5. One end of these Contact mem'- bers is secured by bolts or screws H6 to the base Ic. The other end of each ci the contact members io provided with a lug to form one-half of respective contact points 520 and 2i, the other half of which is secured to respective endsof a common terminal bar i22 which extends transwhile the automatic starting switch |08 isnormally in the open position. e e ,y

By referring to Figure 27, it will be understood, as previously explained, that with the cut-out switch |536 in the closed position, the relay A|04 is maintained in an energized condition which maintains the gang switch Q5 in the closed position `and thereby maintains a closed circuitfor the respective pump motor 64. Whenit `is desired to stcpthe operation of the motor 64 andthe pumps actuatedthereby, it is only Vnecessary to open the respective cut-out switch |06 which will cause the relay |04 to becomede-energized and thereby permit the gang switch 95 to move to the open position and open the motor circuit, and for this purpose, there'is provided a throw-out trip kmember |26 which is, as shown in Figure, so'positioned as to open the cut-out switch and stop the corresponding motor at the end ofthe bombardment zone. This throw-out tripv member |25, in this instance, consists of a base plate |2-composed of any suitable insulating material andv which is secured-by yscrews |2S to a supporting bracket |29 secured to the vertical wall of the base n Mounted on the baseplate |21 is a U-shaped latch bracket `|30 having a pair oi side plates |3|V secured to opposite sides thereof. Pivotally secured to the side plates |3| at |32 is a latch member |33. which is mounted in proximity to one of the legs as |34 of the bracket |30 and arranged so that said leg will form a stop for limiting the pivotal movement ofthe latch |33 in one direction, as illustrated in Figure 21.

The latch is yieldingly maintained against said lug so as to extend outwardly in a radial direction from the machine base by a spring-actuated plunger |35 which h as one end thereof pivotaily connected to the latch |33 rand the other* end slidably mounted in a guide bushing |36 secured A to the opposite leg as |31 of the bracket |30.

The outer end of the latch |33 is arrangedrto extend in the path of movement of the cam ||4 of` each cut-out switch member |06 so thatas each cut-out switch is moved past the throw-,out trip member |26, said-switches Vwillfbe4 opened thereby suiciently to open thev circuit leading through the relay |04 thereby causing said reiay to be deenergized and permit the gang switch 95 toassume the open position and cut off the supply of current to the respective pump motor. Y g In order that the pumps may be automatically 7started to operate again after the evacuated ,tubes have been replaced b-y fresh tubes and before vthese ytubes enter I the oven 22, which operation will hereinafter be more fully described, there is provided a starting `trip member |30 which isposil tioned, `as rshown more particularly ahead of the throw-out trip member |26 intermediate the bombarding zone and the inlet of the oven22. This starting trip member |39 is constructed substantially in the same manner as the vthrow-out tripy |26 and, therefore, the different parts thereof have been given the same reference numerals asthe throw-out trip member |26 and need nottherefore, be further described.

The starting trip member 39 is mounted similarly tothe throw-out trip member |26 except that lthe starting trip member is positioned so that the latch |33 thereof will be in the pathof Amovementof the cams |5 of each starting switch in Figurey 5,

1lil

Viii

i se" secured in place andfto the brackets by a.

V degree of vacuum in the doneV when the machine is to be shut down so as the tubes are sealed ofiv and the remainder of Y the tubulations are removed from the respective exhaust ports, the now open exhaust ports will enter the oven with the pumps connected there- Withinoperative, which will thus prevent the damaging' action of otherwise drawing the hot air from` the oven into the pump system.

` YBy referring to Figure 2'7, it will be evident that the closing of the starting switch, when the oontacter 95 is in the open posltioii, will establish a.

' circuit from the terminal |03 through the starting switch |08 and line |01 and then through the relay |04 to the ground line of'the'motor circuit. will cause the relay |04 to tie-energized which in turnA will bring the contactar 95 to the closed position and Vthereby reestablish the circuit through the respective pump motor 54, and-it is vident that this motel Circuit will Closed as longV as the relay v condition will be maintained after the 4starting switch |||8 has returned toV the open position by A'the current passing through the switch contact member 99, line|05,"cutout'switch |05 and line I1 until such time as the cut-out switch |86 is again opened by the action ofthe throw-out trip member lis.V

Tube carriage Y VThe vacuum pumps 55fmay be of any-wellkl'iownconstruction adapted to produce a high tubes and, therefore, it is not necessary herein to illustrate or describe these pumps n'detail. The suction 'of each of the vacuum pumps 65 is provided with a nozzle 55 which is connected to a respective Yexl'liauzit |40 secured to the tube `carriage Aas |4| on the rotating table 45 in the following novel manner: The tube'carriage |4|-,V in this instance, consists of an annular vl'later manifold |43 'formed of a plurality of, this ,lnsieiiee eight, hollow segments |44 rectangular incross section and maintained in fixed operative relation end to Vend beneath the fixedtable I2 and in vertical alignnicht With the slot 2`IV in said fl'xed table by Vmeans b'fa plurality of, in this instance eight; brackets These brackets |45 are arranged on'e 'at each of the meeting ends 'ofthe adjacent segments,-

as 'shown more clearly in Figures 5 and 26V. Each Vyol these brackets is provided Vwith a. slot inthe upper surface thereof of substantially the saine width and depth asthe manifold |43 for recei'v'- ing the ends of thel adjacent manifolds which are oever plate |45'v which extends over the't'o'p of the manifold ends and is secured by screws or otherwise to the bracket proper. l

Each of the manifold brackets |45is b'y' screws |46'to the outer end of a horizontally disposed a'rm |41 which Vextends outwardly in ya radial direction from the columnfl Vin a planeV some distance above the rotor table 45.

arms |41 are secured to lthe rotating table 45 in uniformcircu'm'ferential spaced relation to 'ing posts or brackets |48 and |49. brack- 04 remains 'energized whichV posed of glass the table 45l beneath a 4respective arm |41l and are secured to the'table at one end while the other ends of 'these brackets are secured `to a respective arm |41, as indicated more particular- 1y 111 Figure 4LV Each of the manifold segments |44 is provided with a Vplurality of, in this instance ve, vertiealopenin'g's |50 therethrough arrangedin uniform spaced relation circumferentially about the manifold and in a plane midway between the `side walls` thereof, see Figures 8,`10 and 26. In each of the holes |50 is secured ina liquid-V tight manner, a. anged bushing whichhas ixlounted therein a vertically disposed exhaust tube' |52 composed of rubber or other resilient material. These tubes |52 are each removably secured in the respective bushings vby means of acollarV |53 composed of brass or other suitable material and which has a loose sliding fit in the lar isoi less diameter than the tube |52 for frictionally engaging said tube, as shown in Figures 8 `and 10.

Each of these exhaust tubes |52v is removably secured in the respective bushings |5| by means of a resilient retaining member |54 whichfin this ihstanc is composed of spring wire bent to form a .rectangular outline of suiiicient size to extend beyond the peripheral edge of thev bushing |5|, while the ends of the wire are arranged in spaced relation at one side of the rectangle and are inserted through respective diametrically opposed holesprovided inthe flange of the bushing |5| and extend into an annular peripheral groove |58' provided near the outer end of the bushing IBI, while the opening through the colcollar |53,'as shown more particularly in Figures l aand 2st The tubes |52 each have a central openingV as |55 extending longitudinally therethrough, vof

substantially the same or of slightly lessrdiam-r Vends of said tubes extend some distance below theV manifold |43 and are connected with respective suction nozzles 65 of the adjacent vacuum pumps 85 by means of a tubular trap |51 coml or other suitable material. The trap |51, in this instance, is composed of two tubes- |58 and |59 of diierent cross sectional areas.` The smaller tube as |58 extends through 'oneend of the outertube |59 and has the inner end thereof extending to within a relatively short distance of the opposite end of the outerftube |59 while-the other end of the tube |58 extends beyond the tube |59 to form the inlet of the trap, and is secured in thelower end of the central opening |55 'of the tube |52.

The outer tube |59 of the trap ls also provided with 'a laterally projecting tube |59 'which extends at right angles to the inner tube |58 from that end of the outer tube through which the w inner tube passes and is connected Withthe rethrough the tube |59as indicated by arrows Z,

4to the wires positioned vthrough the iilament to the mercury cup posi- Figure 8, through the outlet |59 and tube |60l to the respective pump- 65.

The lower end of the trap E51 is positioned in a spherical vessel |62 also composed of glass or like material adapted to contain a suitable cool# ing element such as liquid air which is normally maintained at a level above the lower end of the trap |51 as indicated by the dotted line L in Figure 8 for the purpose of maintaining the lower end of the trap at a very low degree of temperature for cooling and condensing the heated gases being drawn from the tube and thereby assisting in maintaining a very high degree of vacuum in the vacuum tube being exhausted.

The upper end of the vessel |62 may be provided with a cover as |53 provided with a cen-v tral opening therethrough for receiving the'lower end of the trap |51 and which may have a relatively tight connection with the trap |51 and vessel |62 for the purpose of preventing the de composition of the cooling element contained in the vessel |62 to the maximum degree.

The vessel |52 may be removably maintained in operative `relation with the trap |51 by any suitable means such as a spring-actuated bracket |65 having a plurality of, in thisinstance three, upwardly extending diverging arms |55 adapted to engage the vessel |52, the bracket being slidably mounted in a swinging arm |66 which is pivotally connected at |61 to a bracket |68 secured to each pump 65.

Secured to the upper end of eachbushing i! in the manifold |43 by screws i'l is a terminal support |1| composed of any suitable insulating material, see Figures 8, 9 and 10. Each ci these supports |1| has its-opposite side walls provided with an inwardly extending slot [i2 in which is positioned a terminal block |13'cor'nposed preferably of stainless steel and which have `an inner chamber |14 extending downwardly from the vupper surface thereof. l Y` lThe outer vertical wall of each of the terminal blocks |13 extends a relativelyv short distance beyond the adjacent face of the-terminal support 41| and is provided with a longitudinally ex tending horizontally disposed slot |15 for receiving therein one end of a respective pick-up brush |16 which has the other end thereof extending rearwardly and normally spring-pressed outwardly for slidably engaging the adjacent pick-up bar or track i8 or I9. Y

The upper end of each terminal block chamber |14 is enlarged to form `an annular recess for supporting therein the upper end of a mercury cup |18 which is adaptedto extend downwardly into the respective chamber ill-i. VThese mercury cups |18 are for the purpose of receiving the terminal wires of the tubes during the evacuating process for the purposeof electrically connecting them with a source of potential so that these wires may become heated for the purpose of driving the gases out of the coating of the Viilament, and in order that this connection may be readily made without the use of clamps, screws or the like, the cups are partially lled with a 'conducting liquid such as mercury so that when an electric circuit is connected with, for instance, the outer pick-up ring i8, current will pass through the outer brush |15 to the respective terminal block |13 and thence through the mercury cup |18 and mercury contained therein in said cup; thence tioned at the inner side of the terminal block;

.thence through the respective mercury cup |18 land terminal block |13 and pick-up brush |15 to the inner positioned pick-up bar I9.

As hereinbefore described, the pickfup bars or tracks i8 and I9 extend from within a short distance Within the inlet end of the oven 22 around through the oven and to within:a short distance of the discharge end of the Ybombardment zone, and in order that derent voltages may be applied to the filaments as the tubes are moved through the oven and bombardment zone, the outer pick-up ring or track I8 is made up of segments as I8', see Figures 5,'5 and 7. These segments I8 may be made of any desired length and are joined together in insulated spaced relation by means of a tie block |80 composedof suitable insulating material which is secured by any suitable means to the outer insulating ring l5 of theiixed table l2.

The adjacent ends of the segments 'I8' are, arranged in spaced relation when assembled Land each of the tie blocks |88 is provided on its innen vertical face ywith an inwardlyl extending tongue I 88' which extends inwardly between thesel adjacent ends of the segments I8' to maintain said c segments in insulated spaced relation. In order that each of the segments may be suppliedvwith a pre-determined voltage, We have shown aplurality of, in this instance ten, electric conducting wires 8| which are connected with respective pick-up segments I8 as illustrated in Figures 5 and 8. These wires |8| may be maintained ,in iixed relation with the stationary table 2 in any suitable manner as by a series of brackets |82.

Each bracket |82 has the inner end thereof provided with a terminal |84 which is connected with a respective wire |8| and by a metal strap |85 to a respective segment I 8. 'Ihe other end of the wires |8| may be Aconnected with any suitable source of potential including a transformer not shown whereby the voltage for each segment i8 may be quickly and easily changed independently of the remaining segments, to produce the proper heating of the filament as the i tube is movedv through the oven 22. The voltage of the current supplied to( the tube filaments i together, and in either case,the'pickup bar I9 is provided with one or morek ground wires as |86 for electrically connecting said bar with a *circular return bar |86 secured to the brackets I 9 and which in turn, is electrically connected with the transformer in any well-known manner to complete the circuit through the laments.

Cooling system In order that vthe tube exhaust ports and particularly the mercury cups |18 may be maintained at a relatively cool temperature and to eliminate the escape of mercury fumes which would otherwise be caused by heating, a cooling agent such as water may be supplied tothe manifold |43 and to each of the mercury cups in the following manner: An annular vat |81 is mounted adjacent the column 4 upon the inner ends of the manifold supporting arms |41 to rotatewith said arms and manifold, as illustrated more particularly in Figures 1, 4, 5, 25 and 26. 1 i v `notshownI While the other end is provided with a downwardlyk extending portion adapted'to direct the water into the vat |81 Yas said vatis being rotated by the rotary table v45. In order` to prevent the. overflow of the water in the vat |81 in case the water is suppliedthereto faster than. it isk being discharged, there is provided a pair of overflow pipes |90 arranged at diametrically opposite sides of thevat and which have their upper endspositioned a shortdistance belowthe upper edger of the vat |81 and," extend downwardly through said vat with-the lower ends thereof extending into an overflow vat |9|.

The overflow vat |9| is'an annular vat similar V to the vat |01 and is secured in any suitable manner tothe column 4 intermediate the receiv.- ing vat |81 and the'rotary table 45, as illustrated more particularly in Figure 4. Any suitable means may be employed for,` connecting the overflow vat |9| with a drain or source `of supply as the" outlet pipe |92.

` YConnected with thelower portion of the inlet vat |81 at diametrically opposite sides thereof and 'in thisV instance. in the `,vicinity ofthe overflow pipes |90, is one end of an outlet conduit |94 which is connected at the other end to thewater manifold |43 adjacent .one end of one of the segmentsr thereof, as shown more particularly 'in Figures 125 and 26 for the purpose of supplying water to said manifold. In order` that water may circulate from these 'segments tothe remaining segments of the manifold, there has been provided a water connection comprising a U-shaped Vtubular member |96 which has the ends thereof connected kwith adjacent ends of the segments for by-passing'the water around the closed ends of said segments. f v- Y The end of Ythe segment adjacent the-segment to'which the water inlet is connected is provided with an outlet conduit |91 similar to the inlet conduit and which has the discharge end thereof` connected with the respective overflow pipe |90 intermediate the'nlet vat |81-and overflow vat |9|, as shown in Figsj 25 and 26 so that water entering the inlet pipe as |88 andvdischarged into the vat |81 will flow from said vat through the manifold inlet conduits |94and enter at diametrically opposite sides of the water manifold |43. The waterthen flows through the manifold in the direction of rotation thereof and from one segment tothe other through thejoining conduits` |96 to the opposite side of the manifold Where it A gis discharged Ythrough the outlet conduit |91 and overflow pipe |90 to the overflowj vatV |9| Y and thence out through the outlet pipe |92 thereby maintaining a fresh supply of cooling liquid to the manifold at all times.

In order that coolingliquid may be also sup- -plied tov each of the terminal blocks and mercury .cups contained therein, each ofthe terminal blocks in the terminal support adjacent the inlet conduits |94 is connected with/the interior of themanifold by means of a flexible conduit |90 and, a .tube |99,V said tube extending through a suitable openingl provided in the rear end wall ,ofthe terminal support I1 and having the inner end thereof screw-threaded or otherwise'mounted `in an opening provided in the vertical wall of the respective termina-1' block |13 incommunicatio'n aoco/n1 with the chamber |14, as shown more clearly in Figures 25 and 26.

YThe opposite side of said chamberV is provided with a similar tube 200 connected therewithand which extends outwardly through an opening in the forward end ofthe terminal support |1|,and

Vis connected by a suitable flexible tube or hose 'portions of the water manifold with the lastpositioned terminal support connected with theV interior ofthe respective `manifold segment by outlet conduits 202 similar to the inletV conduits |98 and which communicate with the interior of said segment near the outlet conduit |91 of said segment. It is now evident that the water en,- tering the water manifold |43 Vat diametrically opposite sides thereof, will not only pass through f said manifold but will also vbe forced up through the inlet conduits |98 due tothe pressure provided in the inlet vat |91 and through -each of the Yterminal block chambers |14 and about the mercury cups contained therein and lthereby maintaining the mercury in said cups ata sufciently' cool degree of temperature to prevent `theescapement of any mercury fumes which might otherwise-be discharged. i i

Bombardmenf carcae The carriage as 204 visutilized to support the inbefore mentioned, adjacent the exit end of the oven 22, see Figure 1. The carriage 204, as illustrated in Figures 28 to 33'inclusive, consists of a pair of sidebars 206 arranged in radial spaced relation one at either side of the slot 21 provided in the vstationary table |2. 'Ihese bars are slightly p curved longitudinally to conform with the curvature of said slot and are joinedrtogether'- by ra Y plurality of, in this instance two, U-shaped end -cross bars 201 and four intermediate U-shaped suiiicient spaced relation from the uppersurface of the table l2 by supporting brackets 2| secured in any suitable mannerk to the tablev I2 tof permit the free movement of the'carriage over said table.

A coil-supporting plate 2|2 composed .of insulating material is positioned longitudinally of the carriage 204 over the transverse portion of the cross bars 201 and 208 to which the plate is secured by screws 2 I3 or by other suitable means. YThis plate 2 I2 is for the purpose of supporting a plurality of, in this instanceflve, pairsrof bombarding and flashing coils 205V arranged in transverse spaced relationV longitudinally` of rthe carriage 204. These coils are Veach composed of copper tubing or the like coiled in aat spiral with theV outer ends 2|4 thereof extending upwardly through'a respective slot 2|5 formed in Vbombardment; coils 205 and 1S positioned, as herethe vertical edge of the coil-supporting plate 2|2 and then bent at substantially right angles to `extend substantially half way over the plate 2|2 where it is coupled with the corresponding end of the companion coil by a union 2|6 to form a continuous passage for a cooling liquid such as water, from one coil 205 to the other. coil of the corresponding pair.

The other end 2|l of each coil is bent toI extend outwardly from the interior ofthe coil and may be connected as is the case with the inner positioned coils of the first, third and fifth pair of coils by a flexible tubing as 2|8 to a suitable source of fluid supply such as a pipe 2 I9 connected with a cooling tank and force pump, not shown, supplying distilled water, see Figure 1, so that cooling fluid as distilled water may be supplied to the coils. Others of these centrally located coil ends 2 I7, as those of the inner positioned coils of the second and fourth pair and of the outer coil of the fifth pair, are connected by a iiexible tubing 220 to a respective return pipe 22| which are adapted to convey the fluid from the coils to the cooling tanks as indicated in Figures 1 and 25. I'he remaining ends 2|'l of these coils, that is, the centrally located ends of the coils of the first and second, and the third and fourth pairs, are connected by tubes 222, see Figures 1 and 32, so that water entering the water supply pipe |88 may pass through the pipe or conduit 2|9 and flexible tubes 2|8 to the center of the innermost coils 205 of the first, third and fth pairs of coils and will then circulate through said coils, and in the case of the iirst and third pairs, will pass to the outer positioned coils of said pairs and thence through the tubing 222 to the second and fourth pairs of coils respectively and thence out through the outlet tubing 220 and conduit 22| to the cooling tank, and the water entering the fifth pair of coils will pass through said coils and be returned by the respective tubing 220 and conduit 22| to said cooling tank for maintaining said coils in a relatively cool vdegree of temperature during the bombardment operation.

Each of these pairs of coils 205"is maintained in uniform spaced relation on the carriage by a pair of split brackets 224 which are composed of insulating material and are arranged one at either side of the respective union 2| 0 and are bolted or otherwise secured to the upper face of the coilsupporting plate 2|2, as illustrated in Figures 28, 30 and 31.

The pairs of coils 205 are spaced apart, in this instance, a distance equal to the circiunferential spacing of the tube sockets |40 so that as the tubes are being moved forwardly from the oven 22, each pair of coils will be brought into operative alignment with a respective tube whereby the metallic elements of the tube will be heated by a powerful high frequency current induced by said coils, and for this purpose, the coils may be connected in any well-known manner to a suitable sourceof potential not Shown.

The coils 205 of each pair are spaced apart, see Figures 3G and 3l, a distance which will permit the free movement of the tubes therebetween and at the same time, produce the maximum degree of efficiency; that is, each pair of coils 205 is arranged at a given relation te the tubes for effecting the maximum degree of treatment of a specific element in the tube Vand for this purpose, the coils are arranged in three groups. The first group comprises the first pair of tubes 205'; the second group consists of the second and third pair of coils and the third group is composed of the fourth and fifth pairs of coils.

The first group of coils is arranged to bring the center of the coils 205 and, therefore, the center of the ilux in the plane of the cup of the vacuum tube to de-gas said cup by heating the same. The second group of coils is somewhat elevated above thefirst group to bring the center of flux in the plane of the plates of the tubes to heat and de-gas said plates and the third group of coils is arranged at the same level as the first group for the purpose of again heating the cups of the tubes to such a degree as to cause the flashing of the contents thereof.

In order that the value of the current supplied to each group of coils may be altered or controlled independently of the other groups of coils for obtaining the desired degree of temperature of the tube elements effected thereby the coil groups mai be connected in circuit with an adjustable bombarder of any well-known make not herein necessary to illustrate. As an example, theV current supplied to the first group of coils may have a value of 150 amperes which will heat the cup sufficiently to drive out the occluded gases but not to such a high degree of temperature as to nash the cup.

The second group of coils may be subjected to a current of 100 amperes which will produce a heat by induction suilicient to de-gas the plates, while'l the current supplied to the third group of coils will flash the cup at 125 amperes.

in order that the cups may remain in operative relation with each group of coils, a suflicient length of time to obtain the desired result, each pair of coils is caused to travel a certain distance with the tubes, in this instance, substantially equal to the distance between two tube sockets |00 and then move rearwardly to the direction of rotation of the tubes into operative relation with the next and succeeding tube, and for this purpose, there is secured to the upper surface of the tube-supporting manifold |43 substantially -midway between the adjacent tube sockets |40,

a drive bar 226 which has one end thereof 226' up-turned to engage a detent 221 pivotally connected at 228 to a supporting bracket 229 secured by screws 230 to the outer side rail 206 of the carriage 204 intermediate the ends thereof.

The detent 22! extends forwardly from the pivot 228 and is yieldingly maintained in the normal down position against a limiting stop or pin 229 by a spring member 230 which is secured at one end to an offset portion of the bracket 229, as illustrated more clearly in Figure 34.

The forward end 221 of the detent 221 is tapered downwardly and rearwardly for the purpose of engaging a trip bar 23| secured to the top of thestationary table |2 ahead of the detentsupporting bracket 229 and having the inner end thereof in a plane above the drive bar 226 so as to permitthe free passage of said drive bar beneath the trip bar. Therear vertical edge as 23| of the inner end of the trip bar 23| is beveled, as indicated in Figure 35, and positioned in the path of movement of the beveled edge 221 of the detent 221 so that as the carriage 204 is being moved forwardly by the engagement of one of the drive bars 220 and detent 221, the detent will be disengaged from the respective drive bar as the cam portion 221 thereof rides upon the beveled portion 23| of the trip bar 23| 'whichwill permit the carriage 204 to be returned to the starting position by any suitable means as,

for instance, a weight 232 slidably mounted in a guide tube 23.3 which may be secured inany suitable manner to the floor or support for the apparatus and which is connected by a. flexible cable 234, link 235 and bracket 236 to the carriage 204, I

YThe bracket 236V is shown, inthis instance, as being connected to thev outer side rail 206 of the carriage near the rear end thereof, and the ilexible cable 234 is shown as passing over a suitable guide pulley 231 which is rotatably mounted in a supporting bracket 238 secured to the stationary table` |2, said cable passing downwardly through a suitableaperture 240 provided in the adjacent portion of the stationary table I2. y

The carriage 204 is normally maintained in the rear-most position againstthe action of the weight 232 by means of a limiting stop 24| secured to each track rail 2 I0 near the rear ends thereof and which is adapted to be engaged by the respective lugs of the rear end cross bar 201, as

. illustrated in Figure 32. rIn order to cushion the rearward movement of the carriage 204 when coming in contact with the stop 24|, a suitable exible buier member 242 composed of yielding material such as rubber, may be positioned in the weight guide tube 233 at the bottom thereof in the path of movement of the weight 232 as it approaches its lowermost position.

The relation of the carriage stop 24|, detent v 306. 22.1, drive bars 226 and the trip bar 23| are such that when a tube emerging from the Voven 22 comes into operative alignment with Vthe first pair of Vcoils 205 positioned at the rear of the carriage 204,-the carriage 204 will be moved forwardly by the engagement of the detentV 221 and one of the drive bars 226 maintaining the coils and tubein operative relation until the carriage and coils have been moved forwardly substantially the distance between two tubes', whereupon the detent 221 will be engaged by the trip bar 23| which will release the carriage 204, and permit it to be returned to the starting position by the'action of the weight 232 and as the drive bars 226 are provided one for each tube, this movement of the carriage and coils will be repeated for each tube emerging from the voven 22.r

5 Seal-off mechanism burners 245 mounted in opposed relation at the forward end of a U-shaped supporting frame 246.

This frame consists of a pair of burner-supportin'g blocks 241 secured to the forward ends respectively of a pair of horizontally Vdisposed rock arms 248 Ypivotally mounted intermediate their 'ends upon a shouldered screw 249 secured to the forward ends of thecarriage side bars 206 which are extended forwardly beyond the forward end cross bar 201 for this purpose. Y

' The rear ends of the yrock arms` 248 are provided kwith weights 250 for counterbalancing the forward end of the torch frame to permit the ready pivoting movement of the frame about the pivots 249 for a purpose presently described.

*The burner-supportingblocksf241, in this instance', are each provided with a bore 25| in communication with the respective burner 245. These bores 25| are also connected with each other "by means of an inverted U-shaped tubular yoke 252 which uhas its ends secured in respective blocks 241 .and'zwhich is of sumcient'height'andwidth to permit the free passage ytherethrough of. any vacuumV tube for which theimachin'e is designed.'

The fuel,.as a mixture of gas and air, may be supplied tothe burners 245 in any suitable manner as by aexible conduit 253 'which hasone end thereof vconnected to aicorrugated hose connection 254 which, in turn, is connected .withV one of the blocks 241 in communication with the respective bore 25|. The other end ofthe conduit 253 may be connected, as shown more particularly in Figure 1, with a pipe or conduit 255 which is connected with the air inlet pipe 381 and also through the medium vof a second 'conduit 256 and pipe 35 with the gas supply conduit.

It is now evident that themixture of 'gasand air entering through the conduit 253 into the 25| connectedl therewith will pass outwardly 253 is connected, may be providedwithV arvalvey for controlling Vthe supply Yof fuel to the burner connected therewith Vwhich,'in this instance, consistsof the screw 251 screw-threaded in said bore so as to be Vbrought intomore or less` closing relation with the port as 258 leading fromthe bore to said burner as. shownfmore particularly in Figure 37. C Any suitable meansfmaybe employed for igniting the gas escaping from the lburners 245 and which, .in` this instancaconsists of an electrode 259 connected at one end by a screw 260 in insulated relation with the frame 246 and which has the other end thereof positioned in slightly spaced relation with the outlet endof one of the burners 245, which constitutes the other electrode? and lother electrode thereby igniting the gas escaping from said burner. In order that the flame produced at 'the bumers245 may not injure the `vacuum tube `during the 'seal-oil' operation, thereV is provided a pair of shield plates 264 which-are` arranged in a horizontal plane transversely ofv therjrame 246 over the burners 245 with their outer. ends secured to the respective burner supporting blocks'241r, and their inner ends terminating in spaced relation substantially 'midway between said blocks, the inner ends of these plates V264 being spaced apart a distance slightly greater than the diameter ofthe seal-ofi tube as Xof the vacuum tubes Y being evacuated. The rear edge of the inner ends of each shield plate 265 is extended rearwardly and downwardlyrto form respective .guides 264' .for engaging the lead-in the shield plates-246 below the base ofi the tube as 

